This invention relates to methods of assembling rotating machines and more particularly methods of assembling permanent magnet dc machines to obtain accurately set rotor air gaps.
When assembling permanent magnet dc machines it is important that the rotor air gap be accurately set. However, when motors or generators are made in large quantities it is desirable to have generous tolerances on individual parts. It is not desirable to have these tolerances result in large variations in rotor air gap size from machine to machine.
Fine adjustment of air gap size by deformation of the pole pieces which serve as flux guides is not practical since the pole pieces have to be massive to carry sufficient magnetic flux. To allow compensation for the situation in which the air gap in a machine is not accurately set, it is necessary to provide sufficient magnetic material and copper windings for the worst case so that minimum operating specifications can be met. A larger than desired air gap would require additional magnet material and copper windings to achieve the same performance as a machine with a properly set air gap.
It is an object of the present invention to provide a method for adjusting for tolerances individual machine parts of dc permanent magnet machines during assembly, to achieve accurately set rotor air gaps.
It is another object of the present invention to reduce the magnet material and copper needed in manufacturing a dc permanent magnet motor of a given rating.